#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=5e4+1000;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
LL a[maxn][6];
int main(void){
   	cin.tie(0);std::ios::sync_with_stdio(false);
    LL t;cin>>t;
    while(t--){
        LL n;cin>>n;
        for(LL i=1;i<=n;i++){
            for(LL j=1;j<=5;j++) cin>>a[i][j];
        }
        LL ans=0;
        LL p[6];
        for(LL j=1;j<=5;j++){
            p[j]=1e18;
        }
        for(LL i=1;i<=n;i++){
            LL res=0;
            for(LL j=1;j<=5;j++){
                if(a[i][j]<p[j]){
                    res++;
                }
            }
            if(res>=3){
                ans=i;
                for(LL j=1;j<=5;j++){
                    p[j]=a[i][j];
                }
            }
        }
        for(LL i=n;i>=1;i--){
            LL res=0;
            for(LL j=1;j<=5;j++){
                if(a[i][j]<p[j]){
                    res++;
                }
            }
            if(res>=3){
                ans=-1;break;
                for(LL j=1;j<=5;j++){
                    p[j]=a[i][j];
                }
            }
        }

        cout<<ans<<"\n";
    }
   	return 0;
}
